ColdFusion explained

ColdFusion is an application server and software development framework used for the development of computer software in general, and dynamic web sites in particular. In this regard, ColdFusion is a similar product to Microsoft ASP.NET, Java Enterprise Edition or PHP.

Overview

The primary distinguishing feature of ColdFusion is its associated scripting language, ColdFusion Markup Language (CFML), which compares to JSP, ASP.NET, or PHP and resembles HTML in syntax. "ColdFusion" is often used synonymously with "CFML", but it should be noted that there are additional CFML application servers besides ColdFusion, and that ColdFusion supports programming languages other than CFML, such as server-side Actionscript and embedded scripts that can be written in a JavaScript-like language, known as CFScript.

Originally a product of Allaire, and released in July 1995 - ColdFusion was originally developed by brothers JJ and Jeremy Allaire. In 2001 Allaire was acquired by Macromedia, which was in turn acquired by Adobe Systems in 2005.

ColdFusion is most often used for data-driven web sites or intranets, but can also be used to generate remote services such as SOAP web services or Flash remoting.

ColdFusion can also handle asynchronous events such as SMS and instant messaging via its gateway interface, available in ColdFusion MX 7 Enterprise Edition.

ColdFusion provides a number of value-added services out of the box. Among them:

• conversion from HTML to PDF and FlashPaper
• client-side code generation, especially for form widgets and validation
• platform-independent database querying via ODBC or JDBC
• data retrieval from common enterprise systems such as Active Directory, LDAP, POP, HTTP, FTP, Microsoft Exchange Server
• client and server cache management
• session, client, and application management
• file indexing and searching service based on Verity K2
• XML parsing, querying, and validation
• Server clustering
• GUI administration
• Task scheduling

Other implementations of CFML offer similar or enhanced functionality, such as running in a .NET environment or image manipulation.

Early versions

The first version of ColdFusion (then called Cold Fusion) was released on July 10, 1995. This first version was written almost entirely by one person, JJ Allaire. Primitive by modern standards, early versions of ColdFusion did little more than database access.

All versions of ColdFusion prior to 6.0 were written using Microsoft Visual C++. This meant that ColdFusion was largely limited to running on Microsoft Windows, although Allaire did successfully port ColdFusion to Sun Solaris starting with version 3.1.

Releases

1995 Allaire Cold Fusion version 1.0
1996 Allaire Cold Fusion version 1.5
1997, Jun Allaire Cold Fusion version 3.0
1998, Jan Allaire Cold Fusion version 3.1
1998, Nov Allaire ColdFusion version 4.0 (space eliminated between Cold and Fusion to make it ColdFusion)
1999, Nov Allaire ColdFusion version 4.5
2001, Jun Macromedia ColdFusion version 5.0
2002, May Macromedia ColdFusion MX version 6.0
2003, Oct Macromedia ColdFusion MX version 6.1
2005 Macromedia ColdFusion MX 7
2007, July 30 Adobe ColdFusion 8

ColdFusion MX

Prior to 2000, Allaire began a project codenamed "Neo", that would rewrite the basis of ColdFusion using Java, which would allow for greater portability among different platforms.

On January 16, 2001, Allaire announced that it would be merging with Macromedia. Shortly after the merger, Macromedia continued with the incremental release of ColdFusion 5.00 and in June 2002, Macromedia released Macromedia ColdFusion MX (6.0), extending the naming convention of Macromedia's line of products. ColdFusion MX was completely rebuilt from the ground up and was based on the Java 2 Enterprise Edition (J2EE) platform. ColdFusion MX was also designed to integrate well with Macromedia Flash using Flash Remoting.

Starting from the MX (6.0) release, ColdFusion is compiled to bytecode, like JSP and ASP.NET. The compiled .class files are readily accessible, and are cached until their source changes, like JSPs.

With the release of ColdFusion MX, the CFML language was also extended to support basic OOP.

ColdFusion MX 7

With the release of ColdFusion 7.0, the naming convention was amended, rendering the product name "Macromedia ColdFusion MX 7". CFMX 7 added Flash-based, and XForms-based, web forms and a report builder that output in Adobe PDF as well as Flash Paper, RTF and Excel. The Adobe PDF output is also available as a wrapper to any HTML page, converting that page to a quality printable document. The enterprise edition also added Gateways. These provide interaction with non-HTTP request services such as IM Services, SMS, Directory Watchers, and an asynchronous execution. XML support was boosted in this version to include native schema checking.

ColdFusion MX 7.0.2, codenamed "Mystic" includes advanced features for working with Adobe Flex 2.

Current Version

On July 30, 2007, Adobe Systems released ColdFusion 8, dropping "MX" from its name. During beta testing the codename used was "Scorpio". More than 14,000 developers worldwide were active in the beta process - many more testers than the 5,000 Adobe Systems originally expected. The ColdFusion development team consisted of developers based in Newton, Massachusetts and Bangalore, India.

Some of the new features are the CFPDFFORM tag, which enables integration with Adobe Acrobat forms, some image manipulation functions, Microsoft .Net integration, and the CFPRESENTATION tag, which allows the creation of dynamic presentations using Macromedia Breeze - now called Adobe Acrobat Connect technology. Also the ColdFusion Administrator for the Enterprise version ships with built-in server monitoring. ColdFusion 8 is available on several operating systems including Linux, Mac OS X and Windows Server 2003.

Other additions to ColdFusion 8 are built-in Ajax widgets, file archive manipulation (CFZIP), Microsoft Exchange server integration (CFEXCHANGE), image manipulation including automatic captcha generation (CFIMAGE), multi-threading, per-application settings, Atom and RSS feeds, reporting enhancements, stronger encryption libraries, array and structure improvements, improved database interaction, extensive performance improvements, PDF manipulation and merging capabilities (CFPDF), interactive debugging, embedded database support with Apache Derby, and a more ECMA compliant CFSCRIPT.

For development of ColdFusion applications, several tools are available - Adobe Dreamweaver CS3, Macromedia HomeSite+ (nee ColdFusion Studio) and Eclipse. "Tag updates" are available for these applications to update their support for the new ColdFusion 8 features.

Rich forms

ColdFusion Server includes a subset of its Macromedia Flex 1.5 technology. Its stated purpose is to allow for rich forms in HTML pages using CFML to generate Flash movies. These Flash forms can be used to implement rich internet applications, but with limited efficacy due to the ActionScript restrictions in place on Flash forms by Macromedia.

Flash forms also provide additional widgets for data input, such as date pickers and data grids.

In previous versions of ColdFusion, some form validation and additional widgets were available using a combination of Java applets and JavaScript. This option persists for those who do not wish to use Flash, however not all features are supported.

ColdFusion also includes some XForms capability, and the ability to "skin" forms using XSLT.

PDF and FlashPaper generation

ColdFusion can generate PDF or FlashPaper documents using standard HTML (i.e. no additional coding is needed to generate documents for print). CFML authors simply place HTML and CSS within a pair of cfdocument tags and specify the desired format (FlashPaper or PDF). The generated document can then either be saved to disk or sent to the client's browser.ColdFusion 8 has now introduced the cfpdf tag which allows for unprecedented control over PDF documents including PDF forms, and merging of PDFs.

ColdFusion Components (Objects)

ColdFusion was originally not an object-oriented programming language, and even today lacks some OO features. ColdFusion falls into the category of OO languages that do not support multiple inheritance (along with Java, Smalltalk etc.). With the MX release (6+), ColdFusion introduced the component language construct which resembles classes in OO languages. Each component may contain any number of properties and methods. One component may also extend another (Inheritance). Components only support single inheritance. With the release of ColdFusion 8, Java-style interfaces are supported. ColdFusion components use the file extension cfc to differentiate them from ColdFusion templates (.cfm).

Remoting

Component methods may be made available as web services with no additional coding and configuration. All that is required is for a method's access to be declared 'remote'. ColdFusion automatically generates a WSDL at the URL for the component thusly: http://path/to/components/Component.cfc?wsdl. Aside from SOAP, the services are offered in Flash Remoting binary format.

Methods which are declared remote may also be invoked via a HTTP GET or POST request. Consider the GET request as shown.
http://path/to/components/Component.cfc?method=search&query=your+query&mode=strictThis will invoke the component's search function, passing "your query" and "strict" as arguments.

This type of invocation is well-suited for AJAX-enabled applications. ColdFusion 8 introduced the ability to serialize ColdFusion data structures to JSON for consumption on the client.

The ColdFusion server will automatically generate documentation for a component if you navigate to its URL and insert the appropriate code within the component's declarations. This is an application of component introspection, available to developers of ColdFusion components. Access to a component's documentation requires a password. A developer can view the documentation for all components known to the ColdFusion server by navigating to the ColdFusion URL. This interface resembles the Javadoc HTML documentation for Java classes.

ColdFusion and Java

standard ColdFusion installation allows the deployment of ColdFusion as a WAR or EAR file for deployment to standalone application servers, such as Macromedia JRun, and IBM WebSphere. ColdFusion can also be deployed to servlet containers such as Apache Tomcat and Mortbay Jetty, but because these platforms do not officially support ColdFusion, they leave many of its features inaccessible.

Because ColdFusion is a Java EE application, ColdFusion code can be mixed with Java classes to create a variety of applications and utilize existing Java libraries. ColdFusion has access to all underlying Java classes, supports JSP custom tag libraries, and can access JSP functions after retrieving the JSP page context (GetPageContext()).

Prior to ColdFusion 7.0.1, ColdFusion components could only be used by Java or .NET by declaring them as web services. However, beginning in ColdFusion MX 7.0.1, ColdFusion components can now be utilized directly within Java classes using the CFCProxy class.

Recently, there has been much interest in Java development using alternate languages such as Jython, Groovy and JRuby. ColdFusion was one of the first scripting platforms to allow this style of Java development. There are, however, some limitations to ColdFusion's ability to offer Java scripting:

• lack of Bean Scripting Framework plugin support
• one cannot extend Java classes in ColdFusion
• ColdFusion MX 6.1 did not support usage of null value method parameters
• ColdFusion components cannot be consumed in Java as regular classes (see the paragraph on CFCProxy above)

ColdFusion and .NET

ColdFusion 8 is the first version to natively support .NET within the CFML syntax. ColdFusion developers can simply call any .NET assembly without needing to recompile or alter the assemblies in any way. Data types are automatically translated between ColdFusion and .NET (example: .NET DataTable ColdFusion Query).

A unique feature for a J2EE vendor, ColdFusion 8 offers the ability to access .NET assemblies remotely through proxy (without the use of .NET Remoting). This allows ColdFusion users to leverage .NET without having to be installed on a Windows operating system.

The move to include .NET support in addition to the existing support for Java, CORBA and COM is a continuation of Adobe ColdFusion's agnostic approach to the technology stack. ColdFusion can not only bring together disparate technologies within the enterprise, but can make those technologies available to a number of clients beyond the web browser including, but not limited to, the Flash Player, Adobe Integrated Runtime (AIR), Mobile devices (SMS), Acrobat Reader (PDF) and IM gateways.

Custom tags

ColdFusion provides several ways to implement custom tags, i.e. those not included in the core ColdFusion language. The traditional and most common way is using CFML. A standard CFML page can be interpreted as a tag, with the tag name corresponding to the file name prefixed with "cf_". For example, the file IMAP.cfm can be used as the tag "cf_imap". Attributes used within the tag are available in the ATTRIBUTES scope of the tag implementation page. CFML pages are accessible in the same directory as the calling page, via a special directory in the ColdFusion web application, or via a CFIMPORT tag in the calling page. The latter method does not necessarily require the "cf_" prefix for the tag name.

A second way is the development of CFX tags using Java or C++. CFX tags are prefixed with "cfx_", for example "cfx_imap". Tags are added to the ColdFusion runtime environment using the ColdFusion administrator, where JAR or DLL files are registered as custom tags.

Finally, ColdFusion supports JSP tag libraries from the JSP 2.0 language specification. JSP tags are included in CFML pages using the CFIMPORT tag.

Alternative server environments

ColdFusion originated as proprietary technology based on Web hosting technology industry standards. However, it is becoming a less closed technology through the availability of competing products. Products include Railo, BlueDragon, IgniteFusion, SmithProject and Coral Web Builder and you should only consider best coldfusion web hosting to run your online application.

The argument can be made that ColdFusion is even less platform-bound than raw J2EE or .NET, simply because ColdFusion will run on top of a .NET app server (New Atlanta), or on top of any servlet container or J2EE application server (JRun, WebSphere, JBoss, Geronimo, Tomcat, Resin, Jetty, etc.). In theory, a ColdFusion application could be moved unchanged from a J2EE app server to a .NET app server.

Currently, alternative server platforms generally support ColdFusion MX 6.1 functionality, with minor changes or feature enhancements.

Acronyms

The acronym for the ColdFusion Markup Language is CFML. When ColdFusion templates are saved to disk, they are traditionally given the extension .cfm or .cfml. The .cfc extension is used for ColdFusion Components. The original extension was DBM or DBML, which stood for Database Markup Language. When talking about ColdFusion, most users use the acronym CF and this is used for numerous ColdFusion resources such as user groups (CFUGs) and sites.

CFMX is the common abbreviation for ColdFusion versions 6 and 7 (aka ColdFusion MX).

Technical commentary

IT commentators have offered various critiques of ColdFusion, discussing both the potential advantages and disadvantages of this technology relative to other alternatives.

• Cost: Adobe ColdFusion is expensive compared to some of its competitors, which are almost always free. Even Microsoft-based solutions such as ASP.NET are technically free if you own a PC or server running some version of Windows. The rapid deployment of ColdFusion applications negates the cost of the server, since most applications can be built at manpower savings that significantly make up for the cost of the server. However, there are several free versions of ColdFusion, some with enhanced features.
• Open Source: Many scripting languages such as PHP, Ruby, Perl and Python are open-source. Although the language of CFML itself is documented, Adobe ColdFusion's server code is not viewable or modifiable. However, SmithProject is an open-source CFML parsing engine.
• Syntax: CFML syntax is very different from traditional programming languages, which use a C-style syntax, although this is a key reason for its success. With ColdFusion 8, CFScript can now be used as an alternative to all ColdFusion tags.
• Extensions: ColdFusion libraries and extensions are not always free, although there are sites dedicated to open-source ColdFusion code and several open-source frameworks have emerged in recent years in active development. ColdFusion also can easily call Java libraries which alleviates this issue.
• OOP: ColdFusion lacks advanced object-oriented features The release of CF 8 has included a cfinterface tag to define interfaces similarly to OOP languages like Java. such as providing little distinction between instance and class (virtual and static) properties and methods. ColdFusion doesn't offer constructor syntax per se, but rather forces an object factory pattern to return object instances. A common idiom is to use init to indicate a method which is the constructor for each component. Methods are implicitly virtual if they reference the THIS scope. There are several techniques available to provide mixin functionality.
• Scripting: CFScript is similar to but incompatible with the ECMAScript specification. ColdFusion does include some server-side Actionscript functionality (which is ECMA-script compliant), however server-side Actionscript has significantly fewer features than CFML. Note: The release of CF 8 has allowed for more common versions of the scripting syntax. Ex == for equals, < for less than, and ++ to increment a variable will all be permissible.
• Shared hosting: Certain features of best ColdFusion such as event gateways, creation of datasources, caching settings and classpath additions are not readily configurable for usage in a shared hosting environment. The release of CF 8 has allowed hosting providers to provide application specific settings and administrator accounts, which should help to bring more functionality to shared hosting customers. Also, features like Event Gateways are included in the standard version now.
• Bootstrapping: ColdFusion is not a general purpose programming language. It cannot be used to create certain kinds of programs or software. For example, ColdFusion was written in Java and it would be impossible to write ColdFusion in ColdFusion itself (a technique known as Bootstrapping). Extending ColdFusion therefore frequently relies on also using other general purpose programming languages.